It has been 10 years since the U.S. Supreme Court last issued a landmark ruling expanding gay rights in America.

It came in a 2003 case called Lawrence v. Texas. In striking down a Texas anti-sodomy law, the high court declared that intimate sexual conduct between consenting adults was off limits to government regulation.

The author of that decision, Justice Anthony Kennedy, was well aware that he'd just delivered an extraordinary victory to gay rights advocates. Nonetheless, he included an unusual disclaimer near the conclusion of his opinion.

Justice Kennedy said the court's decision that day would have no wider application in the looming showdown over same-sex marriage.

The justices have agreed to examine whether same-sex couples are entitled to be treated equally.

"Today's opinion dismantles the structure of constitutional law that has permitted a distinction to be made between heterosexual and homosexual unions, insofar as formal recognition in marriage is concerned," he wrote.

Now, a decade later, the nation is about to find out who was right—Kennedy in his limiting disclaimer or Justice Scalia in his dire warning.

On March 26 and 27, the U.S. Supreme Court is set to hear two potential landmark gay rights cases, both dealing with the issue of same-sex marriage.

This marks the first time in 40 years that the high court is being asked to fundamentally redefine what marriage is in the United States. In the process, the high court is injecting itself squarely into one of the most divisive social issues of the past quarter century.

The outcome could affect hundreds of millions of dollars in federal marriage benefits currently limited to heterosexual spouses.

As in 2003, gay rights advocates are again hoping to win the potentially decisive swing vote of Kennedy. They are also hoping that the substance of Scalia's impassioned constitutional analysis in his dissent back in 2003 holds true in 2013.

"Lawrence was a very important turning point. It removed a huge roadblock on the path to gay marriage," says Dale Carpenter, a University of Minnesota Law School professor and author of “Flagrant Conduct: The Story of Lawrence v. Texas.”

Specifically at issue before the high court this month are two measures that seek to preserve the traditional definition of marriage.

The first is a 2008 ballot initiative in California known as Proposition 8, which defines marriage in the state constitution as a legal union of one man and one woman. The second case is a challenge to the 1996 federal Defense of Marriage Act, or DOMA, which for purposes of federal benefits also defines marriage as a union of one man and one woman.

Lawyers challenging the measures argue that Prop. 8 and DOMA violate the rights of same-sex couples by treating them like second-class citizens. "With the full authority of the state behind it, Proposition 8 sends a clear and powerful message to gay men and lesbians: You are not good enough to marry. Your loving relationship is not equal to or respected enough to qualify to be called a marriage," writes Washington lawyer Theodore Olson in his brief seeking to overturn Prop. 8.

On the other side, lawyers counter that it is proponents of same-sex marriage who are seeking to change an institution that has existed throughout history as the symbolic joining of male and female. Preservation of this tradition is not discrimination, they say.

"Providing special recognition to one class of individuals does not demean others who are not similarly situated," writes Washington lawyer Charles Cooper in his brief urging the court to uphold Prop. 8. "It is simply not stigmatizing for the law to treat different things differently, or to call different things by different names."

Is marriage a right?

The most basic question at the heart of the debate over same-sex marriage is whether the U.S. Constitution protects a fundamental right to marry regardless of sexual orientation.

Kennedy went on to identify a constitutionally protected zone of personal liberty beyond the reach of the government.

Gay marriage proponents say it clearly does. Supporters of traditional marriage counter that the Supreme Court has never recognized such a right. They cite a 40-year-old precedent, Baker v. Nelson, that upheld a Minnesota law restricting marriage to one man and one woman.

But that's not the precise issue before the court. The justices have agreed to examine whether same-sex couples are entitled—under the Constitution's equal protection provisions—to be treated equally when it comes to marriage and the benefits of marriage.

That's where Scalia's prediction in the 2003 case may prove prophetic, and perhaps decisive. The Texas statute invalidated in 2003 had been justified by state lawmakers as a reflection of society's shared view that homosexual conduct was immoral. Kennedy's opinion rejected the use of sexual morality as a justification for criminalizing a consenting adult's private intimate conduct.

But the court didn't stop there. Kennedy went on to identify a constitutionally protected zone of personal liberty beyond the reach of the government involving the most intimate and private aspects of human relationships.

Kennedy added: "Persons in a homosexual relationship may seek autonomy for these purposes, just as heterosexual persons do."

Because of the Lawrence decision, they can't argue that society views homosexual conduct as immoral. That argument is off the table.

Despite Kennedy's disclaimer that the Texas decision was not about same-sex marriage, the opinion had an immediate and profound effect on the debate over the issue. Within five months, the Massachusetts Supreme Judicial Court declared that same-sex couples in the state enjoyed a fundamental right to marry under the Massachusetts Constitution. It thus became the first state in the US to establish a state-based constitutional right to same-sex marriage.

The first and most frequently cited case in the Massachusetts decision: Lawrence v. Texas. In the years since, eight other states and the District of Columbia have recognized same-sex marriages. At the same time 30 states passed constitutional amendments defining marriage as a union between one man and one woman. Eight other states adopted statutes enforcing the same traditional definition.

Shifting the debate

To prevail at the high court, supporters of California's Prop. 8 and DOMA must be able to offer a persuasive justification for treating gay and lesbian couples differently from heterosexual couples.

Because of the Lawrence decision, they can't argue that society views homosexual conduct as immoral. That argument is off the table.

Instead, proponents of the traditional view of marriage argue that the government is entitled to grant preferential treatment to couples of the opposite sex to encourage what it considers the ideal arrangement for raising children: two biological parents in a stable home, providing male and female role models for their own children.

Traditional marriage supporters contend that the institution would be irrevocably eroded to the detriment of biological fathers and mothers – and children – if same-sex marriages are permitted. Such views are influenced by religious beliefs, biblical teachings, and people's own sense of morality.

Gay marriage proponents counter that same-sex couples are capable of raising well-adjusted children in stable, loving homes just as well as married heterosexual couples. Male-female procreation can't be a qualification for marriage, they say, because infertile couples and the elderly are allowed to wed with no inquiry into their ability or propensity to make babies.

One of the most effective tactics of gay rights activists has been to shift the debate. Instead of asking society to expand its view of marriage to accommodate them, same-sex marriage proponents have attacked those supporting the traditional view of marriage as bigots enforcing marriage exclusivity out of animosity toward gays and lesbians. They compare opposition to same-sex marriage to state laws that once banned interracial marriage, a vestige of the "white supremacy" movement.

In 1967, the Supreme Court struck down Virginia's ban on interracial marriage in a landmark case, Loving v. Virginia. The court said the ban represented invidious racial discrimination in violation of the Equal Protection Clause.

Supporters of traditional marriage counter that the Loving case addresses restricting marriage by race but says nothing about marriage by people of the same sex.

Gay rights activists also argue that same-sex marriage in America is inevitable. They say it is just a matter of time before stereotypes and hostility give way to a more open and compassionate view.

But that argument cuts both ways. Lawyers for same-sex couples seek action in the courts because they say the political system is hostile and rigged against them.

They argue that majorities at the polls, in Congress, and in certain state legislatures are using their political clout to oppress gay Americans and discriminate against them. They cite Prop. 8 and DOMA as prime examples.

Lawyers supporting traditional marriage reject the view that same-sex couples are politically powerless. They note that gay marriage is now recognized in nine states and that the campaign enjoys substantial and growing support from a number of political leaders – including President Obama. For the high court to decide the same-sex marriage debate now with a ruling that would apply nationwide would short-circuit the ongoing political process, they say.

Some conservative analysts compare the situation to the abortion debate, and how the Supreme Court's controversial ruling in Roe v. Wade triggered a generation of turmoil and protest rather than allowing the issue to percolate politically and achieve some measure of compromise.

"We don't think this debate should be prematurely ended by a decree from this court or any other court," says Austin Nimocks, senior counsel with Alliance Defending Freedom, which supports the traditional definition of marriage. "We are asking the Supreme Court to continue to allow communities to go through that [political] process and continue to debate the meaning of marriage, its impact on those communities, and how it should be defined."

Strengthening marriage by expanding it?

Amid all the debate, litigation, and legislation of the past decade, attitudes about same-sex marriage have shifted. In 2003, at the time of the Lawrence decision, 58 percent of Americans opposed same-sex marriage and 33 percent supported it, according to polling by the Pew Research Center. By 2012, the number of Americans opposed to same-sex marriage had fallen to 43 percent, with 48 percent saying they supported the idea.

Many traditionalists are motivated by fears that any expansion of marriage to include same-sex couples will accelerate its demise and encourage other nontraditional unions. There is no doubt that marriage in the U.S. is under siege.

Two generations ago the mere mention of divorce was food for scandal, and the idea of conceiving a child outside a marriage was unthinkable. Today, roughly half of all marriages end in divorce, and nearly 41 percent of American children are born to an unmarried woman.

But some analysts question whether it is fair to blame these monumental shifts on same-sex couples who are themselves seeking the stability and monogamy of marriage and family, and who want to share responsibility for raising the next generation of Americans.

From their perspective, they are not seeking to tear down marriage. Like the opponents arrayed against them, they say they want to help strengthen the institution.

Although the Prop. 8 and DOMA cases are potential landmark decisions, it is unclear how the high court may rule. Like many hotly contested cases before the court, legal analysts say the nine-member tribunal is likely to split 4 to 4 among liberal and conservative justices, with Kennedy holding the margin of victory.

"Many of these briefs might well begin with the words: Dear Justice Kennedy," Professor Carpenter says.

Lawyers for same-sex couples want Kennedy to take up where he left off in the Lawrence decision and establish heightened civil rights protections for gay and lesbian Americans like those for African-Americans and women.

In contrast, lawyers supporting traditional marriage are seeking to channel that part of Kennedy that found it necessary to write the disclaimer in the Lawrence decision.

One of their strongest arguments is that it is not the right time for the high court to intervene in the same-sex marriage debate. Gays and lesbians are beginning to achieve political success at the state and national level, but the vast majority of states still maintain the traditional definition of marriage. There is no critical mass of states seeking change.

By the time the high court declared bans on interracial marriage unconstitutional in the Loving case in 1967, all but 16 states had already repealed their anti-miscegenation laws. In 1960, all 50 states had anti-sodomy laws. By 2003 when the high court declared such laws invalid in the Lawrence decision, 37 states had already repealed their sodomy laws. Only 13 still had them on the books.

Contrast that with the current landscape for same-sex marriage. Nine states, and the District of Columbia, recognize it—but 41 do not. "I'm unaware of Justice Kennedy ever having voted to strike down the laws of 41 states," Carpenter says.

43 years of debate

What will prove decisive? No one knows.

In landmark cases, appearances are sometimes important. It won't help the cause of same-sex marriage that the two lead plaintiffs in the Massachusetts case, Hillary and Julie Goodrich, won their battle to marry but remained together for only two years. Their divorce was final in July 2009.

In contrast, consider the experience of Jack Baker and Michael McConnell. They are the gay couple that sued in Minnesota in 1970 for the right to marry—and lost. The case set a longstanding precedent allowing states to deny marriage to same-sex couples.

"That's the first big court decision on gay rights," Carpenter says. "That couple sued to be married in 1970 when nobody imagined that this was a possibility."

It was a time when most states still allowed the firing of gay people from state jobs, when the federal government would not give gay people security clearances, when gays could not serve in the military, and when police were raiding gay bars.

Despite the hostility of society, rejection by lawmakers, and dismissive rulings by judges, Mr. Baker and Mr. McConnell are still together in Minnesota living as a committed couple—43 years later.

Starkly different perceptions of marriage, coupled with the clash of legal arguments in a country still deeply polarized on the issue of gay rights, make these two of the most watched—and significant – cases before the court in a generation.